Guilin Sun
Ansys Employee

Higher frequency has issues, it might be due to several causes:

too short simulation time, too low mesh accuracy, or PML poor performance.

Please increase the simulaiton time and decrease the autoshutoff min in FDTD/advanced, increase the distance between PML and objects, increase the number of PML layers. Check is there is higher order diffraction. If the Standard PML does not work using its max # of layers, you may need to use other types, such as "Steep Angle PML" with more number of layers.

If you have used override mesh, please make sure it does not increase the default mesh accuracy (by default it is 2). In other words, the override mesh size should be smaller than the background mesh size.

Please do not use "unifrom mesh", or "custom non-uniform mesh" if you do not know the reason.

Please seerch online for those specific terminologies so you will get an idea what they are, if needed.

The forum gives general guidelines so please try to modify and see if there is any improvements.